In their reporting on a vast police spying operation that targeted Muslim New Yorkers, journalists Matt Apuzzo and Adam Goldman homed in on a central challenge facing a post 9/11 America. They wrote in one of a series of stories in 2011: “One of the enduring questions of the past decade is whether being safe requires giving up some liberty and privacy.”

Since Apuzzo, Goldman and other Associated Press journalists who worked on the spying series won the 2012 Pulitzer for investigative reporting, Americans have grown ever more uneasy about the costs of the war on terror. Journalists like Apuzzo and Goldman have given us the information we need in an urgent national conversation.

Now, Apuzzo and Goldman have written a book that digs more deeply into what they came to see as the New York Police Department’s attempt to build its own “miniature CIA.” If you’re a citizen, you need to read “Enemies Within: Inside the NYPD’s Secret Spying Unit and bin Laden’s Final Plot Against America.”

Apuzzo and Goldman frame their narrative within the story of a plot the nation’s largest police department failed to uncover despite compiling maps of where Muslims live in New York, sending officers to take notes on conversations in cafes and restaurants in the city’s Arab neighborhoods and designating mosques as “criminal enterprises” in order to maximize their oversight powers.

“When it mattered most, those programs failed,” Apuzzo and Goldman write after describing how NYPD spies visited Najibullah Zazi’s mosque in New York and the travel agency where he bought tickets to fly to Pakistan for al-Qaida training, but missed the young Afghan immigrant and his radicalization. In 2010, Zazi pleaded guilty to terrorism charges and confessed to plotting to bomb New York’s subway system. The plot was foiled largely by the FBI.

Apuzzo and Goldman quote a supporter of New York Police Commissioner Ray Kelly as saying the NYPD foiled at least 14 Islamic terrorist plots. The journalists question those numbers.

“The NYPD’s combination of publicity and secrecy prevented people from assessing whether its intelligence programs worked and are worth the cost in money and trust,” write Apuzzo and Goldman, who went over hundreds of internal police memos and interviewed intelligence sources.

The Zazi passages can read like padding. But in that affair, the authors have a story worthy of a thriller. The book is peopled with spies, terrorists and decorated war heroes. The prose is declarative and compelling, with touches of humor: “Unlike your typical company … office politics at the CIA were played by people TRAINED to lie, cheat, and manipulate.”

New York police chief Kelly brought in a former CIA analyst to build “a deep roster of undercover officers, a web of informants and a team of linguists and analysts that were unrivaled by any police department in the country.”

The operation, with a budget of $43 million and 400 staffers, took cues from Israel even though, as Apuzzo and Goldman point out, Brooklyn and Queens “were not occupied territories or disputed land.” New York police officers were posted to London, Tel Aviv and Lyon. Really?

Yet, the book is sympathetic to police officials determined, even desperate, to protect a city that had been the target of a devastating terrorist attack. The authors’ most pointed criticism is for those who failed to provide the oversight necessary in our check-and-balance democracy. Politicians and reporters were too quick to simply accept that police were doing the right thing. The FBI, whose agents knew what was going on in New York’s mini CIA, could have opened a civil rights investigation, Apuzzo and Goldman write, but “there was little appetite for such a confrontation.”

I was a reporter in Cairo on Sept. 11, 2001. My Arab colleagues seemed to realize even as they watched TV images of towers crumbling that the attacks would have a profound impact on their lives and their nations. Since returning to the United States, I have seen my fellow Americans grappling with how much they and their country have been changed.

Did, for example, the “security at any cost” mentality of the spy operation help fuel the NYPD’s stop and frisk initiative? In calling for bringing that practice within the Constitution, U.S. District Court Judge Shira A. Scheindlin cited New York Times columnist Charles Blow. Blow says allowing security fears to outweigh Constitutional considerations amounts to “burning down a house to rid it of mice.”